Copolyester resin composition and a process of preparation thereof

Abstract

An aromatic group containing copolyester resin composition which has good biodegradability and physical properties, wherein; (i) 0.1 wt % to 30 wt % of an aliphatic prepolymers having number average molecular weight of from 300 to 30,000; (ii) one or a plurality of aromatic dicarboxylic acid (or an acid anhydride thereof which containing aromatic group in the molecule; (iii) one or a plurality of aliphatic (including cyclic type) dicarboxylic acid (or an acid anhydride thereof); and (iv) one or a plurality of aliphatic (including cyclic type) glycol, wherein the copolyester resin has number average molecular weight of from 30,000 to 90,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 70° C. to 150° C., and melt index of from 0.1 to 50 g / 10min. (190° C., 2,160 g), and the process for preparing and / or producing the same. The composition and preparation method provides a high molecular weight copolyester resin which has good biodegradability and physical properties required for packaging film, trash bags and agricultural film.

Description

The present invention relates to a copolyester resin composition which has good biodegradability and physical properties, and a process for preparing and / or producing the same. More particularly, the present invention have solved a problem of poor biodegradability of aromatic containing copolyester resin wherein the aromatic ingredients are incorporated to increase the physical properties of the copolyester.DESCRIPTION OF THE BACKGROUND ARTThe present invention relates to a copolyester resin composition and a process of preparation thereof which has good biodegradability and physical properties. The conventional aliphatic polyester completely biodegrade in the environment, but they have poor physical properties and inferior processability. To improve the physical properties and inferior processability, the aromatic group is incorporated to the aliphatic polyester, but the rate of biodegradation is greatly decreased because of the aromatic group.The typical polyester resin used for v...

AI Technical Summary

Benefits of technology

Finally, in the fourth reaction step, by polycondensing the polymeric resin which was obtained in the third reaction step, a copolyester resin with number average molecular weight of from 30,000 to 90,000, weight average molecular weight of from 100,000 to 600,000, melting point of from 70.degree. C. to 150.degree. C., and melt index of from 0.1 to 50 g / 10 min. (190.degree. C., 2,160 g) is obtained. This copolyester resin has good processability, physical properties and biodegradability.

Problems solved by technology

The conventional aliphatic polyester completely biodegrade in the environment, but they have poor physical properties and inferior processability.

Such aromatic polyester resins are not degradable naturally so it is a serious. worldwide of environmental concern.

However, the conventional aliphatic polyester resin has a low melting point and a high melt index, because of the structure of the main chain and the crystallinity thereof, and having low heat resistance and unsatisfactory mechanical properties, the usage of this polymer material has been limited.

However, it is difficult to manufacture the aliphatic polyester resins having a number average molecular weight of more than 15,000 using the conventional poly-condensation reaction system because further growth reaction is surpassed by decomposition reaction due to the poor heat stability of aliphatic polyesters.

However, this aliphatic polyester resin has poor processability because of its low weight average molecular weight and low heat stability.

However, the utilization of the polyester resin thereof is very difficult because the physical property such as a tensile strength is poor due to the increased amount of low molecular weight portions.

Furthermore, it is difficult to control the reaction for preparing the polyester resin, because the polyester resin easily becomes a gel type.

However, this process requires more time for the reaction which leads to the poor production yield.

And the isocyanate used as a coupling agent to increase the molecular weight is harmful to the human body so it needs to be handled carefully.

In yet another process, by incorporating aromatic group to the aliphatic polyester, the physical properties have been greatly improved, but the rate of biodegradation gets very slow.

If the reaction temperature is higher than 240.degree. C., the reactant can be decomposed due to thermal degradation.

If the mole ratio exceeds 1.0:2.0, the production cost becomes very high.

If the mole ratio is less than 0.3:0.7, the copolyester resin has low melting point and poor processability.

If the amount of catalyst employed is less than 0.02 wt %, it is very slow to extract the theoretical amount of water, methanol or glycol, or it is impossible to extract.

If the amount of the catalyst employed is more than 20 wt %, the color of the product is poor even though the theoretical amount of water, methanol or glycol is easily extracted.

The conventional aliphatic polyester completely biodegrade in the environment, but they have poor physical properties and inferior processability to apply for the packaging film, trash bags and agricultural film.